Bathyarca philippiana (Nyst, 1848)
Mediterranean. Attached to small stones and gravels by a thin byssus. Continental shelf edge down to bathyal depths.
Original taxon: Arca philippiana.
Synonyms: grenophia, obliqua, obliquata.
Above and below: 600m deep, on white coral bottom, off Fiumicino, Roma, Lazio, W. Italy. 4,2mm.
The binomen Arca philippiana was proposed by P. H. J. Nyst p. 54 of “Tableau synoptique et synonymique des espèces vivantes et fossiles de la familie des Arcacées” (Mémoires de l’Académie Royale […] de Belgique vol. XXII, Brussels 1848) in order to replace Philippi’s Arca obliqua, a junior synonym of Arca obliqua Portlock, 1843.
 
Here is the description given by Philippi: « Testa ovato-oblonga, transversa, gibba, valde inaequilatera antice angustiore postice oblique truncato-rotundata, striis exilibus longitudinalibus, transversisque irregularibus decussata. […] Tota superficies striis radiantibus, confertis, exilibus, interstitia aequantibus, transversisque magis irregularibus decussata. […] Arca angusta. Cardo solitus; antice denticulos circa 5, postice 10 numero. » in Enumeratio molluscorum Siciliae… vol. II, Berlin 1844.

The posterior part shows slightly dominant radial striae. The shape is more elongate than in B. pectunculoides. The ventral margin is a little sinuous. On front view, the valves appear slightly depressed anteriorly.

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